1. Field of the Invention
The present invention relates to a process for treating compositions containing a moist metal or metal compounds, particularly compositions containing extractable compounds which may be easily lixiviated from said compositions and cause pollution. More particularly, the present invention relates to a process of treating compositions comprising at least one solid product separated from the gases evolved during the preparation of steel in steel converters, which solid product comprises at least a metal or metal compound and calcium oxide compound.
2. Description of the Prior Art
In the production of steel, high blowing oxygen in molten iron and adding calcium oxide gases are evolved with products which are removed in a moist washing device and recovered in a precipitation tank in order to avoid environmental pollution due to these products.
In the past, it was possible to recycle the separated products to the blast furnaces wherein iron ore is used. Due to the presence of zinc in the starting iron ore pellets, it is now impossible to recycle the high amount of iron oxide containing separated product to the blast furnaces, as this would lead to unacceptable high zinc concentrations in the latter. This causes difficulties, as zinc evaporates and precipitates onto the controlling apparatus and valves used in the automated blast furnaces, so that operation of the latter is impaired.
On the other hand, this product is also known under the "oxy-sludge" as the product is difficult to handle due to its stickiness after removal of water in an amount as high as possible by means of a vacuum filter, so that this product cannot be used for valuable applications.
Attempts have been made to overcome this disadvantage by adding calcium oxide in order to obtain a product which can be handled more easily.
However, the addition of calcium oxide is relatively expensive in comparison with the value of the product obtained in the form of oxy-sludge. Moreover, the substances present in the sludge after this treatment may still be easily lixiviated, so that in open air storage in open air is impossible.